This invention relates to a method and apparatus for hydraulically transporting objects including objects having a specific gravity greater than one. It is envisaged that the invention will be particularly suitable for hydraulically transporting objects in the form of a quantity of particulate material. The invention is primarily concerned with utilising water as a transporting medium however other liquids may be utilised.
It is already known to hydraulically transport particulate material having a specific gravity greater than one. As a matter of convenience and cost water is normally utilised as the transporting liquid. The material and transporting liquid are combined to form a slurry which is then pumped or otherwise caused to travel along a pipe, conduit or similar supporting structure. There are considerable limitations in attempting to transport particulate material in this manner.
A first requirement is to finely crush the material to provide a particulate material comprised of minute particules to achieve a "pumpable" and otherwise flowable slurry. The finer the particles required the greater is the need to crush and thus the less cost effective the method. Further, the finer the particle size the more difficult it is to de-water the particles at their destination. Thus the transporting of particulate material as a slurry often requires extensive supplementary apparatus and processing both upstream and downstream of the system.
A further disadvantage in utilising a slurry technique is the essentially abrasive nature of slurries. Thus the particle population of the medium must be limited otherwise the friction becomes too high rendering the slurry unpumpable. The friction also manifests itself in the form of abrasive wear on the supporting structure increasing the need for maintenance and replacement. This abrasive nature of a slurry also provides a further disincentive to attempt to pump larger particles as the attrition factor between particles can become self defeating as it tends to reduce the particle size.
A further problem in pumping a slurry is the settling-out of the particles. Settling tends to occur with reduction in the rate of flow, sedimentation resulting with zero flow. Thus a prime mover, conventionally a pump, needs to have a capability of maintaining a rate of flow which will avoid this problem. Should the prime mover fail and the flow stop, the settling of particles can create a deposit which may not clear with reinstatement of the liquid flow. This is a substantial problem with known slurry pipelines and to avoid stand-down time to clear such a blockage auxillary pumps are normally utilised. This problem and the additional cost in attempting to circumvent it also detracts from utilising a slurry approach in the transporting of particulate material.
The aforesaid problems increase with the distance over which transportation is required. This has also tended to limit the utilisation of hydraulic transportation for the carrying of particulate material over extensive distances. For example, very substantial quantities of detritus material such as coal and metal ores often must be transported a considerable distance from their point of extraction. For a variety of reasons conventional transporting means such as railways and road haulage, are becoming less desirable. The provision by this invention of a suitable hydraulic transporting method and apparatus provides a realistic alternative for the passage of such materials over extensive distances.